In recent years, in the fields of, for example, various sensor components for automobiles, components for household electrical appliances, and components for industrial equipment, there has been widely used an aluminum-resin bonded body in which an aluminum substrate formed of aluminum or an aluminum alloy, which has high heat dissipating property, and a resin molded body made of a thermoplastic resin, which has high insulation performance, is light in weight, and is inexpensive, are integrally bonded. In addition, its applications have been broadened.
In addition, hitherto, as the aluminum-resin bonded body in which dissimilar materials, i.e., the aluminum substrate and the resin molded body are integrally bonded to each other as described above, there has been used one in which the aluminum substrate and the resin molded body are bonded to each other with an adhesive agent under pressure. Under such circumstances, recently, as a more industrially suitable bonding method, there has been developed a method involving: inserting an aluminum substrate into an injection molding die; and injecting a molten thermoplastic resin onto a surface of the inserted aluminum substrate, thereby bonding the aluminum substrate and a resin molded body to each other simultaneously with molding of the resin molded body by injection molding of the thermoplastic resin, and there have been proposed some methods of bonding the aluminum substrate and the resin molded body to each other more inexpensively, and further improving bonding strength. In addition, many of such proposals involve subjecting a surface of the aluminum substrate to appropriate surface treatment.
For example, the inventors of the present invention have already proposed: an aluminum/resin integrally injection-molded article characterized in that an aluminum shape and a resin molded body are locked with each other through recesses in an aluminum material and fitting portions in a thermoplastic resin (Patent Literature 1); and an aluminum alloy member excellent in resin bonding property characterized by having protrusions each formed of a silicon crystal (Patent Literature 2).
In addition, for example, there have been proposed: a technology involving integrating an aluminum alloy product, which is obtained through pretreatment involving immersion in an aqueous solution of one or more kinds selected from ammonia, hydrazine, and a water-soluble amine compound, with a thermoplastic resin composition by injection molding (Patent Literatures 3 and 4); and a technology involving subjecting a metal to electrochemical surface treatment using, as an electrodeposition solution, an aqueous solution of a triazinedithiol, or a solution thereof using any of various organic solvents as its solvent, and then bonding the surface-treated metal to a rubber or a plastic (Patent Literature 5). Further, there have been proposed: a technology involving applying an adhesive agent onto a metal plate or forming an organic film by surface treatment, and then integrating the metal with a resin by injection molding (Patent Literature 6); and a technology involving treating a surface of a metal with an acid or an alkali, followed by treatment with a silane coupling agent, and then bonding the metal to a resin by injection molding (Patent Literature 7).